Biological Molecules

Question 1

How does hydrogen bonding occurs in water?

Answer 1

The partially positive hydrogens of one water molecule are electrically attracted to the partially negative oxygen atom of another water molecule.

Question 2

what are the properties of water?

Answer 2

1.In metabolic processes

2.As a solvent

3.High latent heat of vaporisation

4.High specific heat capacity

5.Cohesion

6.Adhesion

7.Density

Question 3

Outline the three condensation reactions of disaccharides ?

Answer 3

1.Maltose forms two a-glucose molecules
2.Sucrose forms a-glucose and fructose
3.Lactose forms b-glucose and galactose

Question 4

what is starch ?

Answer 4

stores energy in plants (starch grains) and is a mixture of amylose and amylopectin

Question 5

What is amylose?

Answer 5

an unbranched chain of glucose molecules joined by 1, 4
glycosidic bonds, as a result of that amylose is coiled and thus it is a very compact
molecule meaning it can store a lot of energy

Question 6

What is amylopectin?

Answer 6

branched and is made up of glucose molecules joined by 1, 4 and 1,
6 glycosidic bonds, due to the presence of many side branches it is rapidly digested
by enzymes therefore energy is released quickly.

Question 7

What is glycogen?

Answer 7

1.main energy storage molecule in animals

2. alpha glucose joined by 1, 4 and 1, 6 glycosidic bonds

3.large number of side branches meaning that glucose & therefore energy, can be released quickly.

4.compact can maximising the amount of
energy it can store

Question 8

What is cellulose?

Answer 8

cells walls in plants

long, unbranched chains of beta glucose joined by glycosidic bonds.

H-bonds between adjacent chains

Question 9

What is the difference between saturated and unsaturated lipids?

Answer 9

Saturated lipids are found in animal fats and don’t contain c-c double bonds whereas unsaturated lipids are found in plants and contains c-c double bonds.

Question 10

The greater the number of unsaturated bonds….

Answer 10

….the weaker the intermolecular bonds resulting
in lower melting point.

so unsaturated lipids are liquid at room temp compared to saturated lipids that are solid at room temp

Question 11

What are triglycerides?

Answer 11

1. are lipids made of one molecule of
   glycerol and three fatty acids joined by ester
   bonds formed in condensation reactions

function: buoyancy, energy store, energy source

Question 12

What are phospholipids?

Answer 12

1. a glycerol molecule, two fatty acids, and a phosphate group

2.Phosphate heads are hydrophilic and the tails are hydrophobic and as a

3. form micelle or bilayer

Question 13

What is the difference between reducing and non-reducing sugars?

Answer 13

Reducing= electron donor

Non-reducing= electron acceptor

Question 14

Outline the benedict’s test for reducing sugars

Answer 14

Add Benedict’s solution.

Heat the mixture.

Observe the colour change- blue-green-yellow-orange-brick red

the stronger the colour of ppt means the higher concentration of sugar present

Question 15

Outline the benedict’s test for non-reducing sugars

Answer 15

If theres no colour change then you must:

Add dilute hydrochloric acid, then neutralise.

Heat and observe colour change- blue brick red

Question 16

Outline the Biuret test- Test for proteins

Answer 16

add NaOH and CuSO4 to sample

colour change: purple for +ve result and remains blue if a -ve result

Question 17

Outline the emulsion test- test for lipids

Answer 17

add ethanol

add water

mix

cloudy emulsion = lipid present

Question 18

Outline the Iodine test for starch.

Answer 18

pipette sample into dropping tile

pipette iodine into dropping tile

colour change from brown to blue black

Question 19

What is the primary structure?

Answer 19

the order and number of amino acids in a protein.

Question 20

What is the secondary structure?

Answer 20

alpha helix or beta pleated sheet

hydrogen
bonding.

Question 21

What is the tertiary structure?

Answer 21

3D shape of the protein- with ionic,disulfide, hydrophobic forces and hydrogen bonds

Question 22

What is the quaternary structure?

Answer 22

final 3D structure with same bonds in tertiary

Question 23

what are globular proteins?

Answer 23

spherical
soluble in water

Question 24

examples of globular proteins.

Answer 24

Haemoglobin- two alpha and
two beta polypeptide chains each containing a haem group(prosthetic group) made of iron(conjugated protein)

Question 25

what are fibrous proteins?

Answer 25

strength and support
insoluble
long

Question 26

collagen as a fibrous protein?

Answer 26

collagen- strong protein due to the types of bonds in its structure, e.g h-bonds and covalent bonds

Question 27

cohesion Vs adhesion

Answer 27

cohesion:
same substances sticking together

adhesion:
2 different substances sticking together